The Yankees have a puzzle. They have huge investments and equal-size physical concerns in their rotation.

What to do?

Pitching coach Larry Rothschild told The Post the Yankees are strongly considering a six-man rotation for September and that it could serve as a precursor for doing it on a longer and larger scale in 2015.

Rothschild cautioned that you have to be able to find enough starters to make a six-man rotation feasible and that upper management would have to buy in. And general manager Brian Cashman said that aside from “talking about it” a bit, the organization is not committed to the concept in the short- or long-term. At least not yet.

However, Rothschild was passionate about trying. “Absolutely” was the word he used to describe if he was serious about attempting this. And not just because myopically he has to figure out how to get the best out of Masahiro Tanaka and Michael Pineda in September and that duo plus CC Sabathia and, perhaps, Ivan Nova next year. But because he sees the epidemic of pitching injuries, particularly the need for Tommy John surgeries, Rothschild says, “I think people are going to have to look at a lot of alternatives.”

Obviously, there are folks still bemoaning the move from four- to five-man rotations. But we are where we are and we are not going back. More guys throw harder than ever before and more guys break down. The cost in days, dollars and playoff chances lost are large. The organizations that figure out how to keep their starters healthy are going to be king.

Consider that 10 teams have used eight or fewer starters this year. All 10 are over .500 and five of the six division leaders have used seven or fewer starters. The average is nine per team, with the Rockies at a major league-high 15 and the Yanks tied for fourth at 12.

Amazingly, the Yankees have not been sunk by their rotation. However, Cashman said, if this season were played out 100 times, the Yankees would not have solved their starting pitching problems in a large majority of them. I am not sure. Pitching is better. Hitting is worse. Thus, I believe you can create some starting pitching depth more readily than in the past. But is there a way to keep key guys healthy? Will starting 26-28 times a season and getting extra rest be better than starting 32-34 times in a five-man rotation?

I am not sure. But I believe it is worth a try and the Yanks are in perfect position to open this laboratory, especially once rosters expand and they have extra relievers in September. On Sept. 2, they begin a phase of 21 games in 20 days. They also hope that during that period they will work Tanaka back into the rotation. His dubious elbow, Pineda’s problematic shoulder and Hiroki Kuroda’s age give them reason to try to provide extra rest.

For next season, taking the huge assumptions Tanaka does not need Tommy John surgery and Sabathia can return from knee surgery, the Yankees have that duo plus Pineda, Shane Greene and, perhaps, a re-signed Brandon McCarthy. That is five. David Phelps and Adam Warren could vie for a sixth spot, at least until Nova returns from Tommy John surgery or Luis Severino, Manny Banuelos or Bryan Mitchell proves ready.

Remember, in Japan most teams have off days each Monday, so starters pitch once a week. During the All-Star festivities, Rangers ace Yu Darvish said MLB teams should shift to six-man rotations to replicate the once-a-week style and take stress off elbows. Subsequently, Darvish was shut down with elbow inflammation.

Can you convince pitchers with bulldog mentalities (like Sabathia) to pitch in a six-man rotation? Because a six-man rotation likely would mean a six-man pen (rather than seven), a team trying this would need players with options so that they could move relievers, primarily, on and off the roster as needed. As with any new attempt in a game of tradition, there will be criticism, unintended consequences and expected bumps. Still, at least for September, the Yankees should open this lab to see what it looks like, particularly because they have Tanaka and Sabathia signed, potentially, through 2020 and 2017, respectively.

“No doubt, you have to see how all the pieces fit,” Rothschild said. “But I think it is something you have to take a look at.”